It is known that the capillary outlet openings of writing instruments, recording instruments, drawing instruments and printers as well as of marking pencils and plotters (said instruments are referred to from now on as writing instruments) are clogged or plugged due to the drying of the marking fluid. The outlet openings of such writing instruments are therefore normally covered by a sealing cap which hinders the evaporation of the volatile components of the marking fluid. In particular the evaporation of the solvent or the solvent mixture is stopped by such a cap in a more or less effective manner.
In case no such caps are put on the capillary outlet opening the marking fluid dries very quickly and plugs the capillary outlet opening.
In order to avoid a fast drying of the marking fluid at the capillary outlet opening or in said capillary outlet opening, respectively, of writing instruments it is known to add liquid additives, to said marking fluids having a low vapour pressure and being hardly volatile. Due to said liquid additives, it is possible after evaporation of the other liquid components of the marking fluid to reuse the writing instruments and to start writing with them again.
Said marking fluids, which are admixed with said known liquid additives, have, however, the disadvantage that they dry very badly on non-absorbing supports or pads, such as foils, glass or metal. A further considerable disadvantage is the fact that the properties of the marking fluid with respect to the surface tension and the viscosity have changed after the more volatile components of the marking fluid have evaporated at the capillary opening of the writing instruments. Consequently the quality of the recording, such as the sharpness of the edge, the penetration of the marking fluid to the backside of the support and the wipe resistance, are reduced after starting writing again until the original mixture of the marking fluid reaches the outlet opening again and flows out of said outlet opening.